Quantitative analysis and clinical application of iris circulation in ischemic retinal disease

Diabetic uveopathy

Diabetes can involve several ocular structures -- including the cornea, lens, and retina -- and cause vascular and neural changes in these tissues. Although retinopathy is the most common ocular complication of diabetes, uveopathy can also be observed. This includes vascular, neural, muscular, and basement membrane changes. The main clinical manifestations of diabetic uveopathy are anterior uveitis and abnormal pupillary dynamics. Fluorescein angiography, optical coherence tomography, and optical coherence tomography angiography are ideal for the imaging of vascular changes of the iris and choroid, while dynamic pupillometry is a simple screening tool to detect neuropathy. Additionally, ultrasound biomicroscopy can provide clear images of the ciliary body. Iris abnormalities, primarily angiopathy and neuropathy, can appear as alterations in vascular diameter, neovascularization, and abnormal pupillary dynamics. Choroidal abnormalities primarily affect blood vessels, including alterations in vascular diameter, microaneurysm formation, and neovascularization. The abnormal manifestations in the ciliary body include a decrease in vessel count, alterations in their diameter, isolated angiomatous dilatation, and diffuse thickening of the basal membrane of the pigment epithelium.

Study on the correlation between iris blood flow, iris thickness and pupil diameter in the resting state and after pharmacological mydriasis in patients with diabetes mellitus

BACKGROUND

To investigate whether iris blood flow and iris thickness at the iris smooth muscle region affect the pupil diameter at rest and after drug-induced mydriasis in patients with type 1 diabetes mellitus (T1DM) and type 2 diabetes mellitus (T2DM).

METHODS

T1DM patients and healthy children were recruited from the SCADE cohort. T2DM patients and healthy adults were recruited from patients undergoing cataract surgery at Shanghai General Hospital. Iris vessel density, pupil diameter (PD) and iris thickness were measured in both the resting and drug-induced mydriasis states. Iris vessel density was measured by optical coherence tomography angiography (OCTA), PD was measured by a pupilometer, and iris thickness at the iris smooth muscle regions were measured using anterior segment optical coherence tomography (AS-OCT).

RESULTS

The study included 34 pediatric T1DM patients and 50 adult T2DM patients, both groups without diabetic retinopathy, and age-sex-matched healthy controls. At baseline, T1DM children and healthy children showed no differences in iris blood flow, iris thickness, or PD. However, the adult T2DM group exhibited higher vessel density at the pupil margin, thinner iris thickness at the iris dilator region, and smaller PD compared to healthy adults, with these differences being statistically significant (P < 0.05). After pupil dilation, there were no changes in iris blood flow and PD in the T1DM group compared to healthy children, whereas the T2DM group showed a significantly smaller PD compared to healthy adults. Multivariate regression analysis revealed that in the T2DM group, glycated hemoglobin was an independent factor of PD after dilation (β=-0.490, p = 0.031), with no such factors identified in the T1DM group.

CONCLUSION

The insufficiently dilated pupil diameter after drug-induced mydriasis is correlated to the level of glycated hemoglobin among T2DM patients.

TRIAL REGISTRATION

The registration number on the clinical trial website was NCT03631108.

Current clinical applications of anterior segment optical coherence tomography angiography: a review

Optical coherence tomography (OCT) is a revolutionary in vivo imaging technology that presents real-time information on ocular structures. Angiography based on OCT, known as optical coherence tomography angiography (OCTA), is a noninvasive and time-saving technique originally utilized for visualizing retinal vasculature. As devices and built-in systems have evolved, high-resolution images with depth-resolved analysis have assisted ophthalmologists in accurately localizing pathology and monitoring disease progression. With the aforementioned advantages, application of OCTA has extended from the posterior to anterior segment. This nascent adaptation showed good delineation of the vasculature in the cornea, conjunctiva, sclera, and iris. Thus, neovascularization of the avascular cornea and hyperemia or ischemic changes involving the conjunctiva, sclera, and iris has become prospective applications for AS-OCTA. Although traditional dye-based angiography is regarded as the gold standard in demonstrating vasculature in the anterior segment, AS-OCTA is expected to be a comparable but more patient-friendly alternative. In its initial stage, AS-OCTA has exhibited great potential in pathology diagnosis, therapeutic evaluation, presurgical planning, and prognosis assessments in anterior segment disorders. In this review of AS-OCTA, we aim to summarize scanning protocols, relevant parameters, and clinical applications as well as limitations and future directions. We are sanguine about its wide application in the future with the development of technology and refinement in built-in systems.

Discrepancies in Vessel Density and Blood Flow Distribution in Different Areas of the Iris among Pediatric Type 1 Diabetes Mellitus and Adult Type 2 Diabetes Mellitus Patients

INTRODUCTION

Diabetes mellitus may compromise the vasculature of the iris, thereby leading to severe vision-threatening complications. This study aimed to investigate differences in iris blood flow indices between pediatric type 1 diabetes mellitus (T1DM) patients and adult type 2 diabetes mellitus (T2DM) patients.

METHODS

This was a cross-sectional study. Pediatric T1DM patients and healthy children were members of the Shanghai Children and Adolescent Diabetes Eye (SCADE) cohort who visited Shanghai Eye Hospital in February 2022. The adult T2DM patients and healthy adults were patients who visited Shanghai General Hospital from October 2021 to January 2022. Iris OCTA was acquired through a Cirrus HD-OCT 5000 angiography system (Carl Zeiss Meditec, Inc.). A unique iris OCTA quantification method was used, and the vessel area density (VAD) and vessel skeleton density (VSD) were obtained. The area from the pupillary margin to the corneoscleral limbus was taken as the whole iris blood flow index, and the inner third near the pupillary margin of the whole iris was taken as the pupillary margin blood flow index.

RESULTS

This study enrolled 34 pediatric T1DM patients, 34 age-matched healthy children, 34 adult T2DM patients, and 34 age-matched healthy adults. The whole iris and pupillary margin VAD and VSD of the pediatric T1DM patients were not different from those of healthy children. The whole iris VAD and VSD of the adult T2DM patients were lower than those of healthy adults, and the pupillary margin VAD and VSD were the same in these two groups. Compared with adult T2DM patients, pediatric T1DM patients had higher whole iris VAD and VSD and lower pupillary margin VAD and VSD values, all with statistical significance. Among diabetic patients, age, BMI, and glycated hemoglobin level were negative independent influencing factors for whole iris VAD and VSD, and age was a positive influencing factor for pupillary margin VAD and VSD.

CONCLUSION

There are diverse alterations in iris vessel density and blood flow distribution between pediatric T1DM patients and adult T2DM patients.